Exhaust gas purifying system of internal combustion engine

(19)

(11)

EP 1 061 245 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	28.11.2001 Bulletin 2001/48

(43)	Date of publication A2:
	20.12.2000 Bulletin 2000/51

(21)	Application number: 00112088.0

(22)	Date of filing: 05.06.2000

(51)	International Patent Classification (IPC)⁷: F02D 41/14, F02D 41/02, F01N 3/20

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

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Priority:

14.06.1999 JP 16670199

(71)	Applicant: Nissan Motor Co., Ltd.
	Yokohama-shi, Kanagawa 221-0023 (JP)

(72)	Inventors:
	Naganuma, Kaname Yokohama-shi, Kanagawa 231-0802 (JP) Tayama, Akira Yokosuka-shi, Kanagawa 238-0043 (JP) Yokoi, Taro Zushi-shi, Kanagawa 249-0003 (JP) Ishihara, Kouji Yokohama-shi, Kanagawa 236-0034 (JP)

(74)	Representative: Schmitz, Hans-Werner, Dipl.-Ing.
	Hoefer, Schmitz, Weber & Partner Patentanwälte Gabriel-Max-Strasse 29 81545 München 81545 München (DE)

(54)	Exhaust gas purifying system of internal combustion engine

(57) A catalyst is installed in an exhaust passage of an internal combustion engine. The catalyst is of a type that traps and stores NOx in the exhaust gas when the air/fuel ratio of the exhaust gas is higher than the stoichiometric ratio and reduces the stored NOx with the aid of reducing components in the exhaust gas when the air/fuel ratio of the exhaust gas is equal to or lower than the stoichiometric ratio. A detector detects operation load of the engine. A control unit includes a microprocessor that is programmed to carry out calculating the amount of the stored NOx when the air/fuel ratio of the exhaust gas is higher than the stoichiometric ratio; judging whether or not the catalyst needs recovering of the NOx-storing ability thereof in accordance with the calculated amount of the stored NOx; determining the amount of NOx to be reduced in accordance with the engine load detected by the detector; and carrying out a catalyst recovering control when the need of recovering the NOx-storing ability is judged. The catalyst recovering control is a control to keep the air/fuel ratio of the exhaust gas at a predetermined lower ratio for a predetermined period.

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